Control Transformer Problems - http://www.hvacmechanic.com/ Forums
Original message
| DeanP
 |  "Control Transformer Problems"
, posted Wed 5 Mar 20:21  
Hello:
I need your help!
Let me preface this by saying I’m not an HVAC guy but I do have some “sparky” experience.
I have a Bryant heat pump/electric furnace that’s driving nuts. The control transformer trips the breaker (on the side of the transformer) and I just can’t seem to isolate the problem. I believe I’ve isolated the problem to the heat pump, but here I’m hitting a brick wall. Here’s what I’ve determined to this point:
With all control wiring in place the transformer trips; some times right a way, sometimes not. If I disconnect the control power to the heat pump from the terminal board at the furnace, the furnace will run fine on AUX or emergency heat. As soon as I reconnect the 24V to the heat pump, the transformer generally trips.
Last week I pulled new control wiring from the furnace terminal board out to the heat pump thinking there was probably a short in the old wiring. This didn’t help – same problem still present.
Next I replaced the heat pump control board. This didn’t help – same problem still present.
Next I unplugged the reversing valve power from the heat pump control board. The heat pump ran until the timer called for defrost. At this point I thought I had found the problem. When I reconnected the reversing valve spade connector on the control board, the valve reversed as it should and didn’t trip the transformer breaker so I let it run all night. It was still working when I left for work the next morning, but had tripped the transformer again by the time I got home. At this point I still thought it might be the valve. I tried running the heat pump again with the reversing valve unplugged from the control board and this time the transformer tripped. Now I’m back to the same problem again.
In one last attempt, today I replaced the contactor on the heat pump. The transformer still trips.
What’s left??????????
Thanks for your help.
Dean
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Replies:
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| DeanP
|  "Re(1):Control Transformer Problems"
, posted Fri 7 Mar 09:50
Houston/bigglen:
BINGO!
A themostat wire was laying against a hot line inside the heat pump and the insulation had melted/worn away and was shorting to the line.
Thanks guys, I really appreciate the help.
Dean
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| bigglenn357
| "Re(1):Control Transformer Problems" , posted Thu 6 Mar 06:23
I agree with Houston,turn power off to indoor&outdoor units and pull top off condensor,check all low voltage wiring inside unit for rubbing and melting against pipes.
Big Glenn
"Imagination is more important than knowledge" (Albert Einstien)
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| Houston204
| "Re(1):Control Transformer Problems" , posted Wed 5 Mar 22:10
A low voltage wire may have shorted to your hot gas line.
"Tip of the Day" Remember to remove power first.
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| | heatpumpguy
| "Re(2):Control Transformer Problems" , posted Thu 6 Mar 11:25
another area to check would be where the wires pass through the control box, have found that lennox heat pumps are bad for shorting there.
heatpumpguy
it's all about the basics
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